Forced convection mass transfer: Part III. Increased mass transfer from a flat plate caused by the wake from cylinders located near the edge of the boundary layer

Enhanced rates of mass transfer in the wake region behind detached cylindrical turbulence promoters were investigated with the use of the naphthalene sublimation technique. The maximum increase in the average rate of mass transfer through laminar boundary layers was over 170%. The remarkable feature of these results was that the enhanced rates of mass trasfer persisted for over one hundred and thirty cylinder diameters downstream from the cylinder generating the wake. The observed effect was not only strongly dependent on the free stream velocity and the location of the cylinders relative to the mass transfer surface, but there were marked differences observed between the rate of mass transfer in the wake region behind one and behind two cylinders. These results resemble a “tuning phenomenon” and are believed to be due to Tollmein-Schlichting instabilities and premature transition.